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Species selection is vitally important for ensuring the success of any ecotechnological solution that may be employed on a particular site. The purpose of this chapter is to provide the engineer with a database of plant species that are suitable for both soil and slope stability by either mechanical or hydrological means, i.e., anchoring and buttressing of deep tap roots; bank and channel reinforcement; deep reinforcement and soil strength enhancement; removing soil moisture, surface protection, shallow reinforcement and erosion control. Protection forests rely on the stability of trees to maintain their integrity especially during storms and with regard to rockfall or avalanches. We therefore provide guidelines as to which species best resist these abiotic forces on slopes. [ABSTRACT FROM AUTHOR]

This chapter concludes the work presented in this book. Future research topics are proposed which include suggestions for developing a database of plant species useful for erosion control and slope stability. Decision support systems also need more work and should be available for the general practitioner to use without specialist training. Field studies and numerical modelling should be combined to answer specific questions, especially concerning large-scale slope instability problems. As economics is an important factor to consider, more research into vegetating hotspots only should be performed. Finally, in today's changing climate, carbon sequestration through vegetation strategies could also be an important line of research. [ABSTRACT FROM AUTHOR]

For centuries vegetation has been used to prevent and control the effects of erosion and mass wasting processes. Techniques have developed continuously until now, when the increased environmental awareness of society has resulted in them being used as key tools in landscape conservation. The need for environmentally friendly techniques to mitigate the problems generated by soil instability (mass movements, rockfall, landslides, etc.) and the incidence of erosion have provoked the appearance in recent years of two different ecotechnological concepts:ground bio-engineering and eco-engineering. Both concepts are complementary, sometimes controversial, and have in common the use of biological materials (live and inert plant materials) as main and essential tools. In this Chapter, an updated and complete review of the different ground bio- and eco-engineering techniques in use is presented. The possible advantages and drawbacks of their application with regard to different degradation factors and processes are pre sented and future perspectives discussed.From the simplest methods such as seeding, mulching or planting, to the most complex ones that integrate different engineering techniques using very different materials (live cribwalls, vegetated gabions, etc.), we describe the uses of vegetation for increasing slope stability and restoring and preserving degraded land. The use of eco-engineering techniques against rockfall and windthrow, relevant problems in many European mountainous areas have also been considered. Finally, the possibilities of combining both eco- and bio-engineering techniques are described. [ABSTRACT FROM AUTHOR]

The hazard assessment of vegetated slopes are reviewed and discussed in terms of the stability of the slope both with and without vegetation, soil erosion and the stability of the vegetated slope from windthrow and snow loading. Slope stability can be determined by using either limit equilibrium or finite element stability analysis methods. The limit equilibrium methods are extended to incorporate the vegetation parameters that are important for the stability of a vegetated slope. The factors that contribute to soil erosion are reviewed and the techniques for assessing and measuring the rate of soil erosion are presented. The assessment of windthrow hazards are comprehensively discussed and a mechanistic model called ForestGALES is introduced which has flexibility for testing many different forest management scenarios. The hazards presented by snow loading on forested slopes are briefly reviewed. [ABSTRACT FROM AUTHOR]

Once the instability process e.g. erosion or landslides has been identified on a slope, the type of vegetation to best reinforce the soil can then be determined. Plants improve slope stability through changes in mechanical and hydrological properties of the root-soil matrix. The architecture of a plants root system will influence strongly these reinforcing properties. We explain how root morphology and biomechanics changes between species. An overview of vegetation effects on slope hydrology is given, along with an update on the use of models to predict the influence of vegetation on mechanical and hydrological properties of soil on slopes. In conclusion, the optimal root system types for improving slope stability are suggested. [ABSTRACT FROM AUTHOR]

This chapter describes the dominant types of processes present on hillslopes where both gravity and running water are active. The impact of natural hillslope processes is important and is currently strongly influenced by human activity due to land use change and vegetation removal, and is becoming even greater due to climate change. Both the fundamentals of erosion and slope stability are discussed in this chapter with respect to processes, causes and impacts. To fully appreciate the role of vegetation in the remediation of adverse slope processes, the fundamentals of these slope processes are addressed. In the first part, the role of mass movements is discussed. The definitions used and physical principles underlying mass movements are explained and keys and diagnostic parameters are given to explain how to recognize certain types of mass movements in the field. The causes of mass movement are described, amongst which deforestation, adverse hydrological conditions or slope undercutting, are summarized. The main types of mass movements i.e. falls, slides and flows are then separately discussed, giving full details with regard to their causes, processes and consequences, as well as a first glimpse to the solutions to slope failure problems, which will be addressed in more detail elsewhere in the book. The second part addresses erosion processes. Accelerated erosion is considered as one of the greatest problems of land degradation as it removes the fertile topsoil at high rates. Mankind, who is removing the original vegetation for agricultural purposes, is causing this problem. Again the general principles behind soil erosion are illustrated, giving attention to the causes and the different soil erosion processes such as sheet erosion, rill and gully erosion, piping and tunnel erosion as well as tillage erosion. [ABSTRACT FROM AUTHOR]

Many different types of natural and artificial slopes exist throughout the world, those that have the potential and suitability for stabilizing by vegetation include earthworks on transport infrastructure, forested and agricultural slopes. This chapter introduces the reader to the different types of natural and artificial slopes and breifly discusses the potential for stabilizing each type of slope with vegetation. [ABSTRACT FROM AUTHOR]

We introduce the terminology used in this book and outline the scientific principles behind the definitions given for ecotechnology, eco- and ground bio-engineering. We focus on the use of restoration and management techniques for slopes prone to shallow mass movement and erosion through natural events such as storms. The use of protection forests is discussed, along with their mechanical stability during wind storms, landslides and rockfall events. Which ecotechnological solution to use in any given situation is outlined, depending on the scale of the problem, economics and the consequences of action and inaction. [ABSTRACT FROM AUTHOR]

Latium, like most other Italian regions, is subject to numerous landslides and gravitational movements. These landslides have been registered and mapped by the Region of Latium. Sixteen sites were chosen for the monitoring of ground bio-engineering projects which are currently being carried out in collaboration between the Region of Latium and the GEMINI Department of the Tuscia-Viterbo University. The monitoring activity was performed by completing a questionnaire for each site. The main data required, in order to have a complete vision of the site and its problems, concerned descriptions of the morphological, lithological and phytoclimatic aspects of the slope. This information was provided by the planners and contractors, who also gave a description of the ground bio-engineering techniques used to stabilize landslides. The aim of this study was to verify the effectiveness of using ground bio-engineering techniques in the Mediterranean climatic zone. In this zone, rooting of plants is especially complicated, but we can exploit the biotechnical characteristics of plants and adapt ground bio-engineering methods to this area. We can use information from this study to protect the territory, whilst minimizing the environmental impact, thus fostering and protecting the environment in areas where ground bio-engineering is carried out. [ABSTRACT FROM AUTHOR]

The procedure for geotechnical site investigation is well established but little attention is currently given to investigating the potential of vegetation to assist with ground stability. This paper describes how routine investigation procedures may be adapted to consider the effects of the vegetation. It is recommended that the major part of the vegetation investigation is carried out, at relatively low cost, during the preliminary (desk) study phase of the investigation when there is maximum flexibility to take account of findings in the proposed design and construction. The techniques available for investigation of the effects of vegetation are reviewed and references provided for further consideration. As for general geotechnical investigation work, it is important that a balance of effort is maintained in the vegetation investigation between (a) site characterisation (defining and identifying the existing and proposed vegetation to suit the site and ground conditions), (b) testing (in-situ and laboratory testing of the vegetation and root systems to provide design parameters) and (c) modelling (to analyse the vegetation effects). [ABSTRACT FROM AUTHOR]

Ongoing and increasing civil engineering and other construction activities in alpine areas pose a threat to local vegetation, soil cover and finally to slope stability. Most of the alpine vegetation communities are fragile and cannot be restored at all. Vegetation establishment is limited by short summers, heavy rain showers, hail, winds, low temperatures and strong UV radiation. The only persisting plants are specialists that evolved and thrive in these conditions. For revegetation at high altitudes thorough planning respecting the site conditions, use of site-adapted or local plant material and appropriate application techniques are essential. [ABSTRACT FROM AUTHOR]

The ability of different types of plants to become established was studied on the road sides of the Egnatia highway, Thessaloniki, Greece.Amixture of perennial plants (grasses, legumes and forbs)was sownat equal quantities without any preparation of the sowed soil surface. Plant density (individuals/m2), above and underground dry weight per individual plant (grams/plant), were measured during the growing season. The results showed that drought tolerant species of all plant life forms had high survival percentages and contributed significantly to the vegetation cover at the end of the growing season. Drought tolerance and the existence of rhizomes benefited the establishment ability of grass species. The best adapted species were the grasses Agropyrum cristatum L., Bromus inermis Leyss., Dactylis glomerata L. and Festuca valesiaca Schleich, the legume Medicago sativa L. and the forb Sanguisorba minor Scop. [ABSTRACT FROM AUTHOR]

The long-term performance of soil bioengineering stabilisation methods in torrent catchment areas is difficult to assess due to their dependence on site-specific factors and the interaction between those factors. In order to gain an insight into the dynamic processes of artificially initialised stands and their protection potential, case studies on hedge brush layers and live crib walls aged up to 60 years were carried out. Both construction types were traditional soil bioengineering methods using rooted plants and live plant material for stabilising and revegetation purposes. The plants were horizontally embedded between layers of fill or slope material. Live crib walls additionally included a box-like arranged timber construction which provides further mechanical stability. [ABSTRACT FROM AUTHOR]

The effect of hydro-seeding, with different combinations of mulching and fertilisation on the establishment of herbaceous vegetation on a slope of mining spoils, were examined during this work. The field trial consisted of four treatments: (A = hydro-seeding, B = hydro-seeding with cellulose plus the EI-1000 organic glue, C = hydroseeding with cellulose plus the synthetic glue CURASOL, D = hydro-seeding plus straw mulching plus asphalt fixing) with three replications. Hydro-seeding only, gave initially poor results, but in the following years these results were similar to those of the other treatments. The combined treatments gave better results initially but statistical differences between them were not identified. The vegetation in the third year was dramatically reduced, at approximately a third of the first year. As result of the fertilisation applied during the fourth year, the vegetation recovered, but to a much lower level than in the first and second year. The vegetation composition was dominated by the sown species in the first year but gradually the indigenous species increased up to 40-50% of the composition in the fourth year. [ABSTRACT FROM AUTHOR]

In the high-mountain region of the Tyrol in Austria, a special method was developed by Huter and Heumader (1981) for the revegetation of soils lacking humus using biennial cover plants. This method shows good results not only under normal conditions, but also on problematic sites such as steep slopes and in subalpine areas. With the exception of fertilizers, no synthetic components, e.g. bitumen emulsions or soil-fixing adhesives are needed. Biennial varieties of rye (Secale cereale L.) and sometimes vetch (Vicia villosa Roth) are used as cover plants, which produce a lot of organic matter above and below ground. These rapidly growing cover plants prevent surface erosion and protect the slowly growing perennial revegetation plants. After 2 years, the rotting shoots and roots form a green manure, which is important for soil microorganisms. Biennial cover plants, perennial revegetation plants and fertilizer are applied together. On steep terrain small ditches (furrows), running diagonally across the slope, are dug or hoed by hand to control surface runoff and prevent surface erosion and the formation of rills and gullies. This method has proved to be cheap and effective and has the advantage of mostly using natural material. [ABSTRACT FROM AUTHOR]

In this study, we examined the current environmental situation and geological-hydrogeomorphological characteristics, as well as the phenomenon of mass land movement in the area crossed by the National Road Thermopylae- Nafpactos (with an emphasis on the road running between Damasta and Skamnos, Ftiotida) Greece.We also depicted the changes and distortions in the condition of the geological-hydrogeomorphological characteristics due to both roadwork and the operation of the road. [ABSTRACT FROM AUTHOR]

The Egnatia Motorway is the largest road currently under construction in southern Europe. It is understood that the construction of such a large-scale project causes both environmental and landscape disturbances. Being sensitive to issues concerning environmental protection, Egnatia Odos S.A. has implemented a series of methods aimed at the aesthetic restoration of disturbed surfaces and the prevention of surface erosion. The above-mentioned goal can be achieved through installation of woody vegetation species on the slopes of the Egnatia Motorway. Therefore, the company uses for restoration forestry species of native flora, which are adapted to the environment of the area to be restored. The company policy is to undertake itself the selection of seeds from various forestry species and produce plants in a nursery. For the collection of seeds, suitable biotopes in the wider project area as well as the species that can be massively produced were identified. The seeds collection were transferred to the company laboratory, cleaned, subjected to quality control and stored. Prior to the use of seeds in the nursery, the necessary pretreatment, depending on the species, was carried out in order to terminate the dormancy and enrich the germination. Meanwhile, the production of plants that were considered difficult to germinate was investigated. Seeding took place in QuickPot propagation trays and the filling materials used were: enriched peat, perlite and soil. During production, all the necessary measures were implemented in order to achieve an excellent planting material. After one year, the plants produced from the seeds in the nursery were transferred to the surfaces to be restored and were planted. The plants were planted near the areas from which their seeds were collected. The installation of vegetation on gunite, aiming at the aesthetic restoration of the landscape (apart from the protection of the slope against erosion), has produced very satisfactory results. [ABSTRACT FROM AUTHOR]

The Egnatia Motorway is the greatest highway infrastructure project currently being constructed in Southern Europe. The construction of such a large-scale project is expected to cause an environmental and hence landscape disturbance. Landscapingworks are, therefore, of a critical importance and are imposed by the Environmental Terms approved for each project. As far as erosion is concerned, the hydroseeding of herbaceous species is a widely used practice for the protection of slopes against surface erosion, which is preferably applied immediately after their final configuration. Undoubtedly, the establishment of woody species immediately after the configuration of the surfaces under restoration (cuts and fills) and at the minimum possible cost constitutes one of the most preferable landscaping solutions in highway construction. In this context, the Green Unit of "Egnatia Odos A.E." carried out an experimental application of woody species hydroseeding, with the purpose of investigating the effectiveness of this method, as far as the establishment of woody vegetation on the Egnatia Motorway slopes in concerned. This application was implemented in two stages. The first one was carried out in cooperation with a group of experts from the Aristotle University of Thessaloniki, at a small scale and after strict experimental planning. The second one was an experimental-pilot application, in order to re-check the positive results of the previous test, to extract more useful conclusions and to check this method in terms of its feasibility as part of the green works performed along the Egnatia Motorway. Another issue, which is closely related to the previous one, is the protection of slopes against erosion by application of various engineering methods using cuttings, apart from hydroseeding and planting. These works, which are compliant with the general environment-friendly philosophy in approaching such issues, are supplementary to the hydroseeding of herbaceous species and are more effective in anti-erosion action when compared to conventional planting works. At the same time, this method serves the need for aesthetic restoration. [ABSTRACT FROM AUTHOR]

A decision support system (DSS) has been developed to assist expert and non-expert users in the evaluation and selection of eco-engineering strategies for slope protection. This DSS combines a qualitative hazard assessment of erosion and mass movements with a detailed catalogue of eco-engineering strategies for slope protection of which the suitability is evaluated in relation to the data entered. The slope decision support system is a knowledgebased DSS in which knowledge is stored in frames containing rules that can evaluate the available information for a project, stored as project specific information in a data file. The advantages of such a system are that it accepts incomplete information and that the qualitative nature of the information does not instil the user with a sense of unjustified exactitude. By its multidisciplinary and progressive nature, the DSS will be of value during the initial stages of an eco-engineering project when data collection and the potential of difierent eco-engineering strategies are considered. The accent of the output of the DSS is on the application of eco-engineering strategies for slope protection as an environmentally friendly solution aiding sustainable development. For its acceptance within the engineering community, the DSS needs to prove its predictive capacity. Therefore, its performance has been benchmarked against successful and unsuccessful cases of slope stabilisation using eco-engineering. The target audience and the areas of application of this DSS are reviewed and the strategies for further development in this area suggested. [ABSTRACT FROM AUTHOR]

A number of landscape projects have been completed around Athens (Greece) for the 2004 Olympic Games. The common purpose of these projects was the promotion of quality in: design, construction and maintenance stages. They also comply with environmental management, which is a method of organising and implementing environmental protection measures. [ABSTRACT FROM AUTHOR]

The increased number of catastrophic slope instabilities in Europe in the last decade highlights the need for integrated management of such occurrences. The decision support system presented here incorporates expert knowledge on slope stability and eco-engineering and represents user-friendly solution for help in decision making process on mitigation of slope instability. Based on the results of field studies, experience of the project partners, theory and case studies available in the literature, the slope decision system (SDSS) is a modern decision support system that promotes use of eco-engineering solutions for mitigation of slope stability problems connected with the uppermost soil horizons. The basic considerations, design aims and objectives, together with the advantages and the disadvantages of the approach are discussed in the light of ever-evolving decision making system theory. The future of eco-engineering decision support systems is also discussed with a special emphasis on the learning component for the end-user. [ABSTRACT FROM AUTHOR]

After a wildfire in a Pinus halepensis Mill. forest, in northern Greece, the burned trees were logged and the logs were removed either by mechanical or animal traction. The effects of logging and log removal methods on soil and vegetation recovery were evaluated comparing the logged sites with a burned but unlogged site and the unburned forest. Fire and logging did not affect the soil pH and caused only a short-term reduction in organic matter content. Two years after the fire, the highest rates of soil loss were observed in the logged area where mules were used for log removal. Soil moisture showed some differences between treatments during the first year after fire but then values were similar. Logging and particularly the use of skidders for log removal caused an initial increase in the amount of exposed bare ground but later when vegetation cover increased differences were minimized. The main woody species showed a species specific response to the treatments and while seeder species were favoured in the unlogged sites the same was not true for the respouters. In general, the growth and survival of pine seedlings was not affected by treatments. [ABSTRACT FROM AUTHOR]

During 1997 a fire destroyed about 62% of the urban forest in the city of Thessaloniki, northern Greece. Between 50 and 80% of the forest vegetation was burned within the watersheds of the six torrents that flowed across the destroyed area. In this area the forest service constructed agrotechnical, and flood-protection works in the streams and the basins of the torrents to prevent erosion and to protect the city from flooding. The agrotechnical works consisted of channelling, drifts of branches and log erosion barriers. In the present study the effectiveness of the operation of the agrotechnical works in the protection of the erosion phenomena is examined. The success of the agrotechnical works are examined 7 years after their construction and the contribution of these works to the natural regeneration of the forest is evaluated. The erosion prevention and flood protection measures that were constructed contribute significantly to the stability of the forestal soil and the protection of floods. Their contributions in assisting the natural reforestation works were also remarkable. [ABSTRACT FROM AUTHOR]

In a Pinus halepensis Mill. forest of central Greece, we studied the effects of two fires on postfire plant community recovery by comparing a site that was burned once and another adjacent that was burned twice. During the first 15 months after fire, we monitored plant species recruitment, plant density and growth. Lower species richness and plant densitywere observed in the site burned twice compared to that burned only once. The growth ofwoody species did not differ between the two treatments and presented high variability even within the same plot. Resprouting plant species appeared earlier than obligatory seeders. Fifteen months after fire, the ecosystem was dominated by the maquis species that existed in the prefire period, mainly Quercus coccifera L., Pistacia lentiscus L., Phillyrea latifolia L., with a low contribution of Pinus halepensis seedlings and a greater proportion of Cistus species (Cistus monspeliensis L., C. creticus L., C. salvifolius L.). [ABSTRACT FROM AUTHOR]

In an experimental beech (Fagus sylvatica L.) coppice plot, throughfall, stemflow and superficial runoff were monitored on a single event basis, in order to verify the short term hydrological balance in different conditions of leaf cover. Rainfall events were simulated using a rainfall simulator, operated at two different intensities. The plot was hydraulically isolated, along its whole perimeter and a small drain, placed in the lowest part of the plot, was used to collect the superficial runoff. Twelve rain gauges were used to survey the throughfall whereas the stemflow was collected through rubber collars. Superficial flows were measured both by sampling the discharges coming out of the plot and by collecting the total water runoff volumes. [ABSTRACT FROM AUTHOR]

Rainfall simulators have been developed as tools for evaluating hydrological and erosive processes due to agronomical activities and have been very rarely used in forested areas. When a rainfall simulator is operating under forest cover, the characteristics of this peculiar environment (high trees, irregular topography, steep slopes, difficulties in supplying water) as well as the gross-rainfall transformation and redistribution on soil surface (as rain is filtered through the canopy) have to be taken into account. [ABSTRACT FROM AUTHOR]

To determinewhich are the most important characters governing mechanical resistance to rockfall and wind loading, static winching tests were carried out on three tree species: Silver fir (Abies alba Mill.),European beech (Fagus sylvatica L.) and Norway spruce (Picea abies L.) in a mixed forest stand. Trees were winched to an angle of 0.25° at the stem base, both up- and downhill in order to compare how the same individual reacts when tested in two different directions. Trees were then winched to failure. Strain gauges were attached to the stem and one up- and downhill lateral root in order to determine the distribution of strain within the tree during overturning. Root morphology was then measured for all trees which uprooted during failure. No significant differences were found in the force necessary to winch trees up- and downhill in any species, either to an angle of 0.25° or to failure. Strain was significantly higher in lateral roots of Silver fir than in roots of Norway spruce and European beech when winched downhill. Downhill roots of Norway spruce were largely held in tension when trees were pulled downhill, whereas in Silver fir and European beech, they were held in compression. When trees were pulled uphill, no significant differences were found between species, and strain decreased along the lateral root of downhill roots only. European beech possessed a significantly greater number of roots than either Norway spruce or Silver fir. Norway spruce possessed a higher proportion of total root length near the soil surface, whereas European beech had the greatest proportion in the intermediate depth class and Silver fir had the highest maximal root depth. Norway spruce had a significantly lower proportion of oblique roots than the other two species, resulting in a plate-like root system which was less resistant to overturning than Silver fir or European beech. [ABSTRACT FROM AUTHOR]

Soil bioengineering is an appropriate approach to deal with erosion problems and shallowseated landslides especially in developing countries such as Nepal. This technique is a cost-effective solution using locally available materials and low-cost labour. Furthermore, this approach allows the involvement of the local population in the management and maintenance aspects. As an example for prevention of soil erosion and increased slope stability by means of vegetation, a landslide in the Middle Mountains of Nepal was selected for an innovative approach of rescheduling the implementation of soil bioengineering stabilisation works into the dry, winter season, testing plants for their suitability and using cut bamboo (Bambusa nutans G. C. Wall.) for the construction of vegetated crib walls. This paper deals with investigation, design, construction and monitoring over a period of 32 months. Soil bioengineering solutions for erosion control and shallow slope instabilities in the Middle Mountains proved to be highly successful and all plants, in particular Salix tetrasperma Roxb. and Alnus nepalensis Don., seemed to be suitable for winter plantation. [ABSTRACT FROM AUTHOR]

Current erosion-control studies in mountainous catchments emphasise the effectiveness of bioengineering works in constructing vegetation barriers that are designed to trap and permanently retain sediment upstream of such barriers. Plant establishment and succession should result in colonisation of these sediment deposits, thereby improving the trapping capacity of the works. The aim of this study is to evaluate the ability of the natural vegetation to colonise and grow on sediment accumulated upstream of 29 bioengineering works. They were constructed on the channel bottom of two marly gullies in the mountainous Southern French Alps region, which has a Mediterranean climate. We analysed the soil seed bank in sediment deposits after a germination experiment conducted in the laboratory, where soil cores were placed in a non-limited water condition. We also determined the standing vegetation which developed on the sediment deposits on field sites over 2 years of drought (2003 and 2004). The results show that the number of plants was 80/m2 on average in the samples studied in the laboratory, vs. 31/m2 in 2003 and 20/m2 in 2004 on the field sites, with a total diversity of 40 species. Therefore, despite 2 years of drought, natural plant colonisation occurred on the sediment deposits. An improvement in soil water conditions slightly increases the capacity of the sediment deposits to allow seed germination. However, despite the initial success in vegetation colonisation, plant abundance and recovery were rather low, which suggests that vegetation established itself very slowly. [ABSTRACT FROM AUTHOR]

The creation of the National Cadastre's map, part of which is the forest cadastre (according to the decision of the Ministry of Agriculture No 99580/506 from 1 July 1999), is based on law 266/1998 ‘National Cadastre and other provisions' and forecasts the use of photogrammetric methods. The changes in land use, and the stretches of mountainous and semi-mountainous abandoned land are represented on these maps. The photogrammetric community is experiencing a transitional period from the analytical to the digital era. This transition is met with prudent enthusiasm, and care as to which digital systems may replace the analytical ones and under what circumstances this change will take place. This paper endeavours to answer such a question. A complete and fully documented answer lies of course, outside the limitations of this project. Here, however, a comparison was attempted between a contemporary analytical photogrammetric instrument and a digital photogrammetic system, which are both of relatively low cost. This choice was made in order to enable the market in this country to assess the limitations and possibilities of such systems, in view of the large-scale cadastral surveys. Therefore, this comparison is not only confined to accuracy, but touches upon other issues, such as reliability, user friendliness and efficiency. There are many factors, not to mention errors, in the photogrammetric procedure. There main causes are the operator, the instrumentation used and various unpredictable factors. The area of study and stereopairs thatwere usedwere chosen so that a reliable terrestrial survey would be available for the purposes of control. A rural forest area and a forest area of Taxiarchi-Vrastamon were selected. For these areas, stereopairs and related diapositives were available at the scale of 1: 20000. They were taken from an E.E.C. GR80-3 (c = 152.25 mm) aerial survey camera with an overlap of 65%. The same control points were used for the orientations on both the analytical low cost system and the digital low cost system. The analytical low cost system is a more reliable instrument than the digital low cost system, because both its repeatability and accuracy are better. [ABSTRACT FROM AUTHOR]

The effect of land abandonment as a result of changing land-use policies is becoming more and more important throughout Europe. In this case study, the role of vegetation succession and landslide activity on steep abandoned slopes was investigated. The influence of vegetation succession on soil properties over time, as well as how developing root systems affect soil reinforcement was determined. The study was carried out in the Alcoy basin in SE Spain, where the marl substratum is prone to landsliding along steep ravines. The bench-terraced slopes have been abandoned progressively over the last 50 years and show various stages of revegetation. The study was carried out at two scales; at the catchment scale long-term evolution of land-use, vegetation succession and slope failure processes were investigated. At a more detailed scale, vegetation cover, soil properties and rooting effects on soil strength were determined. [ABSTRACT FROM AUTHOR]

Vegetation is widely used for the control of surface erosion on slopes but different vegetation types vary in their effectiveness and, in some situations, a vegetation cover can have adverse effects and actually increase the rate of erosion. Where climatic or soil constraints exist, there are also concerns about how quickly an effective cover can be obtained. Simple screening models can be used to indicate the likely severity of these issues prior to designing an erosion-control system. As soon as the canopy cover is higher than 0.3 m above the surface, there is a risk that satisfactory protection against soil particle detachment by raindrop impact will not be obtained. With canopies higher than 1.0 m, detachment rates may exceed those from natural rainfall on bare ground. The amount of vegetation needed to prevent soil particle detachment by surface runoff depends upon the steepness of the slope but, for grasses, a stem density of at least 10,000 stems/m2 is recommended. Uniformity of distribution is important because a clumpy vegetation cover can lead to concentrations of flow between the plants with consequent increases in velocity. A vegetation cover can be used to induce sediment deposition. Where grass is used as a buffer strip, a width of 10-12 m is usually sufficient to trap even the fine sediment. For large areas of the world where water erosion is a problem, it is feasible to establish sufficient grass cover within 1 year. [ABSTRACT FROM AUTHOR]

This manuscript describes the development and application of a fuzzy computer system for the estimation of a longterm unique torrential risk index, expressing as many parameters as possible. This paper describes the estimation of the torrential risk in the areas of Trixonida and Lisimaxia lakes and it is a part of a bigger project for the torrential risk evaluation of the watersheds, lakes and streams of Greece. The model that was introduced to the computer system works as follows: many torrential (morphometric and hydrographic) parameters are used as input to the System and they are evaluated by Fuzzy functions. This produces separate risk indices with each one associated to a specific parameter. Finally T-Norms are applied in order to unify the risk indices and to produce a unified means of risk measure. The computer system has proven its ability to work more effectively compared to the older (established) methods. From these points of view, this work can be considered as an original and important contribution in the international literature. There are no restrictions in the application-area of the system. [ABSTRACT FROM AUTHOR]

The Quercus suber L. woodlands of South Portugal are subjected to numerous attempts of reassessment, in order to control their invasion by shrub vegetation and to prevent fires. Following the intensive soil management techniques, soil is traditionally harrowed in order to establish fodder species, increase aeration and destroy shrubs and other weeds. These practices leave it bare and exposed to erosion for long periods resulting in a poor clay schist soil. In this study, the risk of erosion on Q. suber woodland with different vegetation management techniques was examined. The different blocks were: shrub vegetation left undisturbed for at least 11 years, vegetation destroyed by a rotary cutter mower and enrichment with fast growing herbaceous species after tillage. To estimate soil degradation, several soil physical and chemical properties were studied. Graphical interpretation of these soil properties was performed using geostatistics. Ordinary kriging was the geostatistical technique used for the creation of maps, which were then introduced into a geographic information system (GIS) and their values reclassified. Spatial modelling was then applied using the revised universal soil loss equation and the superimposed maps developed a final overlay map for potential soil erosion. On the superimposed final map of erosion risk, the areas with highest risk of erosion were located. In those areas, the erosion risk could be decreased by suggesting simple changes in the vegetation management such as: keeping tillage only in the lowest erosion risk areas and leaving natural vegetation or enriching the soil with fast growing herbaceous species in high-erosion risk areas. The present research shows that geostatistics are useful for sustainable management of extensive agrosilvopastoral woodlands. [ABSTRACT FROM AUTHOR]

In order to determine the mechanical resistance of several forest tree species to rockfall, an inventory of the type of damage sustained in an active rockfall corridor was carried out in the French Alps. The diameter, spatial position and type of damage incurred were measured in 423 trees. Only 5% of trees had sustained damage above a height of 1.3 m and in damaged trees, 66% of broken or uprooted trees were conifers. Larger trees were more likely to be wounded or dead than smaller trees, although the size of the wounds was relatively smaller in larger trees. The species with the least proportion of damage through stem breakage, uprooting or wounding was European beech (Fagus sylvatica L.). Winching tests were carried out on two conifer species, Norway spruce (Picea abies L.) and Silver fir (Abies alba Mill.), as well as European beech, in order to verify the hypothesis that beech was highly resistant to rockfall and that conifers were more susceptible to uprooting or stem breakage. Nineteen trees were winched downhill and the force necessary to cause failure was measured. The energy (Efail) required to break or uproot a tree was then calculated. Most Silver fir trees failed in the stem and Norway spruce usually failed through uprooting. European beech was either uprooted or broke in the stem and was twice as resistant to failure as Silver fir, and three times more resistant than Norway spruce. Efail was strongly related to stem diameter in European beech only, and was significantly higher in this species compared to Norway spruce. Results suggest that European beech would be a better species to plant with regards to protection against rockfall. Nevertheless, all types of different abiotic stresses on any particular alpine site should be considered by the forest manager, as planting only broadleaf species may compromise the protecting capacity of the forest, e.g., in the case of snow avalanches. [ABSTRACT FROM AUTHOR]

SLIP4EX is a straightforward computer program developed in connection with the EU funded ECOSLOPES project for routine stability analysis and the assessment of the contribution of vegetation to slope stability. The slope section is drawn up and dimensions and parameters are fed in to the Microsoft Excel based program for stability calculations and comparisons of Factors of Safety using different methods of analysis (Bishop, Janbu, Fellenius, Simple, Greenwood). The background and assumptions involved in the derivation of each of the methods is briefly described. The simplicity of the program enables the user to understand the nature of the analysis, explore the parameter assumptions made and compare the different methods of analysis. Soil reinforcement by geosynthetic layers or anchors, and vegetation effects of enhanced cohesion, changed water pressures, mass of vegetation, wind forces and root reinforcement forces are readily included in the analysis. The program is freely available on request from the author. [ABSTRACT FROM AUTHOR]

This paper presents the effects of a landslide on vegetation located on Tymfristos mountain and more specifically in the basin of the Kati stream, Sperchios river. The landslide areas are described and related to the density and the type of vegetation. The woody vegetation developed on the gliding surface was studied using dendrogeomorphologjcal methods. In particular, the direction and tilting degree of trees as well as the deformation of trunks was compared to trees growing on a neighbouring stable surface. Subsequently, the time of mass movement reactivation was estimated using a visual growth anomaly analysis on dominant fir (Abies borisii regis Mattf.) individuals growing on the landslide. From the results it is suggested that the landslide negatively affected fir growth ring width increase at certain times without, however, nullifying it. Certain time periods are identified with intense past sliding phenomena due to increased rainfall that subsequently increased underground water. [ABSTRACT FROM AUTHOR]

When plants are loaded by external forces, whether they be above ground e.g. wind or canopy weight, or from within the soil e.g. soil displacement on slopes, the roots will be mechanically loaded. Exactly howthe plant roots carry loads during these events is unknown because of their complex morphology and the heterogeneity of the root properties. To gain greater insight into plant root-soil mechanical interactions, a series of tests have been carried out to investigate the mechanical behaviour of roots and rubber root-analogues under tension during pull-out from soil. The results of the mechanical tests are augmented by a novel use of image analysis (specifically Particle Image Velocimetry) of sequential digital photographs taken during loading. This allows root and soil movements to be measured during the tests so that more can be learned about the effects of root morphology on the load distribution and deformation behaviour. The testing methodology and philosophy are presented here together with preliminary results. [ABSTRACT FROM AUTHOR]

The influence of root morphology and soil type on the mechanical behaviour of tree anchorage was investigated through numerical modelling.We developed a simple computer program to construct three-dimensional virtual root architectural patterns. This tool was used to build four schematic patterns: heart-, tap-, herringbone- and plate-like root systems. Each of these rooting types was characterised by specific branching characteristics. However, the total volume (proportional to the wood biomass) and material properties were kept constant. The finite element method was used to calculate the mechanical response of root/soil systems when the stem was subjected to bending forces. The overturning resistance of the four schematic root patterns was determined in four different idealistic soil types. These soils were based on Mohr-Coulomb plasticity models. Results showed that soil internal friction modified the position of the rotation axis during tilting of the root/soil plate. Rooting depth was a determinant parameter in sandy-like soils. Overturning resistance was greatest in heart- and tap-root systems whatever the soil type. However, the heart root system was more resistant on clay-like soil whereas the tap root system was more resistant on sandy-like soil. Herringbone and plate root systems were twice as less resistant on clay soils and 1.5 times less resistant on sandy soils when compared to heart and tap-like structures. [ABSTRACT FROM AUTHOR]

Outplanting container-grown oak seedlings with undesirable shoot and root characteristics result in poor establishment and reduced field growth. The objective of this study was to determine the influence of container type on both above-and below-ground nursery growth and field performance of one-year old tap-rooted seedlings Quercus ilex L. and Quercus coccifera L. The experiment was conducted in an open-air nursery and the seedlings were grown in three container types. At the end of the nursery, growth period seedlings' shoot height, diameter (5 mm above root collar), shoot and root biomass, root surface area, root volume and total root lengthwere assessed. Then the seedlings were planted in the field and their survival and growth were recorded for two growing seasons after outplanting. The results showed a difference between the Quercus species in the effect of container type. Q. ilex seedlings raised in paper-pot had significantly greater height, diameter, shoot and root biomass and root volume than those raised in the other two container types. Similarly, Q. coccifera seedlings raised in paper-pot, had significantly greater above-and below-ground growth than those raised in the other two container types. Both oak species showed relatively low survival in the field; the mortality was mainly observed the first year after outplanting, especially after the summer dry period. However, 2 years after outplanting, the paper-pot seedlings of the two oak species showed better field performance. [ABSTRACT FROM AUTHOR]

This paper presents selected results on the above- and below-ground growth performance of 12 indigenous woody species commonly found growing naturally in unstable riparian slope and/or bank environments throughout New Zealand. This study was needed because little information exists on the effectiveness of New Zealand's indigenous riparian plant species for slope and stream bank stabilisation. By examining the growth performance of selected riparian species during the first 5 years following establishment,we provide valuable insights into the likely strengths and limitations of individual species at maturity and, therefore, into their overall potential usefulness, singularly and/or as mixed plantings, for future riparian stabilisation projects. For all species, their root systems are typically shallow and confined to the uppermost 31 cm of soil. Root spread (mean maximum diameter) increased with increasing age with interspecies differences, by age 5 years, ranging from between ~1 and 2.5 m. At age 5 years the mean root biomass, for all species combined, was 1.2 kg/plant, and averaged ~23% of total plant biomass. Changes in the allocation of biomass for root and shoot growth appear to be species and age dependent. The results of this study indicate that most have above- and below-ground growth attributes well suited to colonising steep and unstable riparian slopes where shallow soil failure is prevalent and/or where stream banks are rocky with skeletal soils. All form part of the early plant succession. Once established, and in the absence of grazing, they are relatively fast growing. The effectiveness of riparian restoration programmes using indigenous species, though potentially high for low-order stream, will be limited by their relatively shallow-rooted habit for bank stabilisation on larger rivers without the prior installation of structural protection works. [ABSTRACT FROM AUTHOR]

In the territory of Altomonte, a village located in Calabria, in the Southern part of Italy, a newthermoelectrical station is under construction. Thiswork involved major earthworkswhich regarded newexcavated slopes. In order to protect soil from erosion due to rainfall and runoff and also in order to prevent superficial soil instability, it was decided to plant four different species of perennial "gramineae" plants (Eragrass, Elygrass, Pangrass and Vetiver) characterised by deep roots. Works began in November 2002 and ended in May 2003, a period marked by very different climate and meteorological conditions, varying from exceptionally rainy and cold winter to warm and dry spring months. The paper describes the different stages of the project and the monitoring programme for the following months. The extension of the work and the use of four different kinds of vegetation made periodic inspections of the entire site appropriate. Two in situ investigations, respectively performed in August 2003 and in November 2003, are outlined. The aim of these surveys was to confirm the success of the work by verifying the growth of the plants and roots. The principal monitored parameters were the percentage of sprouted plants, the height of the foliage and the depth of roots. The investigations showed good results, keeping in mind the very difficult climatic conditions and the extreme poor fertility of the topsoil laid down upon the clay layer: in particular, high survival rate were measured over the entire area of the works and the root systems have developed sufficiently to grow through the upper topsoil layer (0.2-0.3 m) into the underlying clay layer. In March 2004, a sampling programme was undertaken on the same site. Direct shear tests were carried out in the laboratory in order to evaluate the increase in shear strength of the rooted soil mass. The research involved the recovery of three undisturbed samples of soil with roots for each of the four types of ‘gramineae' plants and three undisturbed samples constituted only of soil, from the surface to a depth of 1.0 m. The tests were performed in a large direct shear apparatus on 200 mm diameter samples. The test results allowed to evaluate the roots' contribution of the different gramineous species and to underline the direct correlation between the increase in soil shear strength and the root tensile strengths. In particular, an increase in cohesion ranging between 2 and 15 kPa was recorded, according to the different species: the maximum values of increase in shear strength were reached by Vetiver roots, which are also characterised by the highest tensile strength. [ABSTRACT FROM AUTHOR]

Three groups of Mediterranean pines were examined to describe the development of root symmetry on sites characterized by shallow soils and low water availability. Sampling included: (1) 3-year-old planted seedlings of Pinus halepensis Mill. taken from Sithonia Halkidiki, northern Greece, (2) 5-year-old natural regenerated seedlings of Pinus brutia Ten. taken from Kedrinos Lofos, Thessaloniki and (3) 65-year-old trees of Pinus brutia taken from Kedrinos Lofos, Thessaloniki. Root system symmetry was examined by measuring the number, the diameter, the cross-sectional area, the root area index and the length of the lateral roots of each root system, and by analyzing their distribution around the stem. Aboveground plant symmetry was also estimated. The findings of the study indicated that there was an asymmetric root system in all three groups that is characterized by the concentration of the main laterals along the contour lines instead of uphill or downhill; however, the asymmetry was much higher in the young plants. This asymmetry was not correlated with the above-ground plant growth form, which was found to be symmetric. The asymmetric development of root can be attributed to the shallow soil and the high mechanical resistance of the underground bedrock that stopped the taproot growth, restricted the root penetration in the deeper layers and obliged the roots to elongate towards the surface soil layers, where there is more available water. [ABSTRACT FROM AUTHOR]

The roots of trees provide an important contribution towards the stability of hill slopes. Tree roots in the soil act very similarly to steel fibers in reinforced concrete and provide resistance to shear and tensile forces induced in the soil. In addition, the roots also absorb water from the soil, which reduces moisture content, again helping to increase the stability of the slope. As Iran has a long history of landslides, our research deals with the effect of tree roots on slope stability, in particular, the following species which are of economic and environmental interest: tea (Thea sinensis L.), citrus (Citrus spp.), lilaki (Gleditshia caspica Dsf.) and angili (Parrotia persica D.C.) (Mosadegh, 1996). The study was carried out in Roudsar Township in Gilan State of Iran. Of the overall surface area of 1800 ha, 288 ha were considered suitable for the purposes of this study. A large part of the area had slopes of steep gradients on which natural vegetation was present. Other parts of the same area have been cleared and planted with tea and citrus crops. Soil samples were taken from an area of approximately 70 ha for testing in the laboratory. Direct shear tests were carried out on soil samples and the factor of safety (FOS) calculated. Results showed that the FOS was increased in soils with tree roots present. The global slope FOS was then determined using Bishop's method. We calculated the FOS in order to protect slopes where the gradient exceeds 25%. In this case study, the minimum FOS was assumed to be 1.3, which corresponds to e.g. Parrotia sp. vegetation with 40-60% crown cover, a soil internal friction angle of 15° and a slope angle of 21°. When soil internal friction angle equals 15° and slope angle is >31°, slope stability cannot be increased by any vegetation species. [ABSTRACT FROM AUTHOR]

The mechanics of root reinforcement have been described satisfactorily for a single root or several roots passing a potential slip plane and verified by field experiments. Yet, precious little attempts have been made to apply these models to the hillslope scale pertinent to landsliding at which variations in soil and vegetation become important. On natural slopes positive pore pressures occur often at the weathering depth of the soil profile. At this critical depth root reinforcement is crucial to avert slope instability. This is particularly relevant for the abandoned slopes in the European part of the Mediterranean basin where root development has to balance the increasing infiltration capacity during re-vegetation. Detailed investigations related to root reinforcement were made at two abandoned slopes susceptible to landsliding located in the Alcoy basin (SE Spain). On these slopes semi-natural vegetation, consisting of a patchy herbaceous cover and dispersed Aleppo pine trees, has established itself. Soil and vegetation conditions were mapped in detail and large-scale, in-situ direct shear tests on the topsoil and pull-out tests performed in order to quantify root reinforcement under different vegetation conditions. These tests showed that root reinforcement was present but limited. Under herbaceous cover, the typical reinforcement was in the order of 0.6 kPa while values up to 18 kPa were observed under dense pine cover. The tests indicate that fine root content and vegetation conditions are important factors that explain the root reinforcement of the topsoil. These findings were confirmed by the simulation of the direct shear tests by means of an advanced root reinforcement model developed in FLAC 2D. Inclusion of the root distribution for the observed vegetation cover mimics root failure realistically but returns over-optimistic estimates of the root reinforcement. When the root reinforcement is applied with this information at the hillslope scale under fully saturated and critical hydrological conditions, root pull-out becomes the dominant root failure mechanism and the slip plane is located at the weathering depth of the soil profile where root reinforcement is negligible. The safety factors increase only slightly when roots are present but the changes in the surface velocity at failure are more substantial. Root reinforcement on these natural slopes therefore appears to be limited to a small range of critical hydrological conditions and its mitigating effect occurs mainly after failure. [ABSTRACT FROM AUTHOR]

The effect of root reinforcement on slope stability has been well researched through empirical studies, but to date few mechanistic studies have examined the influence of tree roots on slope stability. Furthermore, the previous research has lacked consideration of the effect of landslide displacement on root reinforcement. This paper will analyze the influence of root reinforcement on safety factors (Fs) as a function of slope displacement. A model of a root system as a cluster of straight bars inserted from unstable soil into bedrock is used to reliably estimate increases in the shear resistance of the soil. The relationship between root reinforcement and lateral displacement is analyzed under two conditions: ultimate stress and pullout resistance of root fibers. The species used in the present research was the Japanese cedar (Cryptomeria japonica (L.f.) D. Don.), the most common tree species in Japan. The spatial distribution of root size and root inclination was taken from field experiments performed by Japan Sabo Technical Center in 1998. The reinforcement capacity of root fibers is considered as a function of the horizontal displacement of the landslide and the depth of the slip surface. By combining the data obtained from field experiments with a calculation model of inclined roots, this paper analyzes the Ozawa slope safety factor. Thus, root reinforcement and the slope safety factor were calculated for various displacements in the process of landslide movement. [ABSTRACT FROM AUTHOR]

Highway embankments and cutting slopes in the United Kingdom, particularly in the South East of England, are often constructed of or within stiff over-consolidated clays. These clays are prone to softening with time leading to shallow slope failures and costly repairs. Reinforcement by natural vegetation is potentially a cost-effective method of stabilising these types of slopes over the medium-long term. However, there is a lack of information on how natural vegetation reinforces and stabilises clay slopes. To investigate this problem, the potential reinforcement of selected oak (Quercus robur L.) and hawthorn (Crataegus monogyna Jacq.) roots was assessed by conducting in situ root pull-out experiments on a London Clay cutting in south-east England. Pull-out tests were carried out using specifically designed clamps and either a hand pull system with a spring balance and manual recording of force for oak roots or a jacking system with electronic data logging of applied force and displacement for hawthorn roots. Oak roots had a mean pull-out resistance of 7 MPa and that of hawthorn roots was 8 MPa. The electronic data logging of applied force (pull-out resistance) and displacement of the hawthorn roots provided additional data on the failure of branched roots which could be correlated with variations in root morphology. The failure of the roots can be categorised into three modes: Type A: single root failure with rapid rise in pull-out resistance until failure occurs; Type B: double peak failure of a forked or branched root and Type C: stepped failure with multiple branches failing successively. The different types of root-soil bonds are described in relation to root anchorage and soil stability. [ABSTRACT FROM AUTHOR]

Vegetation can significantly contribute to stabilise sloping terrain by adding cohesion to soil: this reinforcement depends on the morphological characteristics of the root systems and the tensile strength of single roots. The paper presents the results of research carried out in order to evaluate the biotechnical characteristics of the root system of three typical Mediterranean plant specieswhich can affect slope stability. The species considered in the present study are Lygeum spartum L. (a perennial herbaceous monocotyledonous), Atriplex halimus L. and Pistacia lentiscus L. (two dicotyledonous shrub species). The plant specimens were collected in the Basilicata region (Southern Italy) by in situ excavation to obtain the whole root systems. Single root specimens for each species were sampled and tested for tensile strength measurement and the complete root systems were analysed to evaluate the root density distribution with depth in terms of root area ratio. The resulting data have been used to calculate the reinforcing effect in terms of increased shear strength of the soil using the model of Wu (1976, Investigation of landslides on Prince ofWales Island. Geotech. Eng. Rep. 5 Civil Eng. Dep. Ohio State Univ. Columbus, Ohio, USA) andWaldron (1977, Soil Sci. Soc. Am. J. 41(3), 843-849), a simple and widespread model based on the reinforced earth theory. The results show that root reinforcement exerted by L. spartum is stronger than the reinforcement exerted by P. lentiscus and A. halimus in the upper layers of the soil, while P. lentiscus presents higher reinforcement values in deeper horizons. A. halimus presents lower values than either of the other species studied. [ABSTRACT FROM AUTHOR]

Vetiver grass (Vetiveria zizanioides), also known as Chrysopogon zizanioides, is a graminaceous plant native to tropical and subtropical India. The southern cultivar is sterile; it flowers but sets no seeds. It is a densely tufted, perennial grass that is considered sterile outside its natural habitat. It grows 0.5-1.5 m high, stiff stems in large clumps from a much branched root stock. The roots of vetiver grass are fibrous and reported to reach depths up to 3 m thus being able to stabilise the soil and its use for this purpose is promoted by the World Bank. Uprooting tests were carried out on vetiver grass in Spain in order to ascertain the resistance the root system can provide when torrential runoffs and sediments are trying to uproot the plant. Uprooting resistance of each plant was correlated to the shoot and root morphological characteristics. In order to investigate any differences between root morphology of vetiver grass in its native habitat reported in the literature, and the one planted in a sub-humid environment in Spain, excavation techniques were used to show root distribution in the soil. Results show that vetiver grass possesses the root strength to withstand torrential runoff. Planted in rows along the contours, it may act as a barrier to the movement of both water and soil. However, the establishment of the vetiver lags behind the reported rates in its native tropical environment due to adverse climatic conditions in the Mediterranean. This arrested development is the main limitation to the use of vetiver in these environments although its root strength is more than suffcient. [ABSTRACT FROM AUTHOR]

Forest vegetation is known to increase hillslope stability by reinforcing soil shear resistance and by influencing hydrologic conditions of soil. Although the importance of plant root systems for hillslope stability has received considerable attention in recent years, the quantification of such an effect needs more investigation. In this paper, we present a synthesis of the data gathered in the last 5 years for some species in different locations of the Alps and Prealps of Lombardy (Northern Italy) with the aim to increase our knowledge on root tensile strength and on root area ratio distribution within the soil. Concerning root tensile strength we developed tensile strength-diameter relationships for eight species: green alder (Alnus viridis (Chaix)D.C.), beech (Fagus sylvatica L.), red willow(Salix purpurea L.), goat willow (Salix caprea L.), hazel (Corylus avellana L.), European ash (Fraxinus excelsior L.), Norway spruce (Picea abies (L.) Karst.) and European larch (Larix decidua Mill.). Results show a great variability among the different species and also for the same species. In general, however, root strength (in terms of tension) tends to decrease with diameter according to a power law, as observed by other authors. Comparing the power law fitting curves for the considered species, it can be observed that they fall in a relatively narrow band, with the exception of hazel, which appears the most resistant. Concerning the evaluation of root distribution within the soil we estimated the root area ratio (the ratio between the area occupied by roots in a unit area of soil) according to its depth for five species (beech, Norway spruce, European larch, mixed hazel and ash) in three locations of Lombardy. Results show that there is a great variability of root density for the same species well as for different points at the same locality. The general behaviour of root density, in any case, is to decrease with depth according to a gamma function for all the studied species. The results presented in this paper contribute to expanding the knowledge on root resistance behaviour and on root density distribution within the soil. The studied location have allowed the implementation of soil-root reinforcement models and the evaluation of the vegetation contribution to soil stability. [ABSTRACT FROM AUTHOR]